WHEN DISCARDS SURVIVE - ACCOUNTING FOR SURVIVAL OF DISCARDS IN FISHERIES ASSESSMENTS

When discards data are included in fish stock assessments, it is gener ally assumed that all discarded animals die. However, there are fisher ies in which a significant fraction of discards are able to survive. T his case can be treated with a simple extension of the usual analytica l model of exploited populations, enabling Virtual Population Analysis (VPA) to be used for parameter estimation. The paper examines the eff ects on estimates obtained by VPA when discards are allowed to survive , and validates a procedure for deriving partial fishing mortalities i n multiple-fleet fisheries where discarding and survival rates are fle et specific.